Abstract

Packaged table water is an important source of drinking water, but bacterial contamination and antimicrobial resistance may compromise its microbiological safety. This descriptive cross-sectional study evaluated the antibiotic susceptibility patterns and the occurrence of genetic determinants for enolase (eno) and antibiotic resistance in bacterial isolates recovered from commercially packaged table water sold in Port Harcourt, Nigeria. The study was conducted over a 12-month period. Bacteria were isolated using standard bacteriological techniques and presumptively identified based on their cellular and biochemical and molecular characteristics. Antibiotic susceptibility was determined using the Kirby–Bauer disc-diffusion method, while polymerase chain reaction (PCR) was performed on ten selected isolates to detect the eno (enolase) gene, as well as the bla and aac(6′)-Ib antibiotic-resistance genes. A total of ten bacterial groups were identified from the packaged table-water samples. The identified bacteria included Staphylococcus spp., Lactobacillus spp., Bacillus spp., Proteus spp., Micrococcus spp., Salmonella spp., Escherichia coli, Klebsiella spp., Enterobacter spp. and Shigella spp. Antibiotic susceptibility varied among the bacterial groups and tested antibiotics. Among Gram-positive isolates, the highest reported susceptibility varied by genus, with relatively higher values recorded for selected fluoroquinolones (pefloxacin, 40.3% in Staphylococcus spp.; ciprofloxacin, 52.2% in Lactobacillus spp.) and gentamicin (47.4% in Bacillus spp.). Among Gram-negative isolates, Salmonella spp. showed the highest reported susceptibility to amoxicillin (85.7%), whereas Proteus spp. generally exhibited low susceptibility across tested agents, with maximum susceptibility not exceeding 30.8% (for amoxicillin) and complete resistance (0.0% susceptibility) to amoxicillin–clavulanic acid, ofloxacin, and cefixime. Molecular analysis detected eno (enolase gene) in 7 of 10 (70.0%) isolates, bla (beta-lactam resistance marker) in 4 of 10 (40.0%), and aac(6′)-Ib (aminoglycoside resistance marker) in 5 of 10 (50.0%). Three of these isolates (30.0%) carried all three genetic targets, while one isolate (10.0%) was negative for all three markers. The findings demonstrated varied antibiotic susceptibility profiles and the presence of genetic determinants for enolase and antibiotic resistance in bacterial isolates from packaged table water. These results highlight the importance of routine microbiological surveillance and strengthened quality-control measures in packaged-water production.